The present invention relates to an air bag door formed in interior materials of various vehicles having a superficial material on a substrate so as to be invisible, a method of controlling breakage of fracture lines of the air bag door, and a method of deploying an air bag when the air bag door is broken.
More specifically, the present invention firstly relates to an air bag door having a fracture inducing device for breaking the substrate and a fracture inducing device for breaking the superficial material so as to break the substrate and the superficial material in a preferred order of breakage by portions synchronously with each other when the air bag is inflated and deployed. The present invention secondly relates to a method of controlling breakage of fracture lines for causing the facture lines of the air bag door to be broken in a desired preferable pattern when the air bag is deployed. The present invention thirdly relates to a method of deploying an air bag for guiding an air bag which is expanded when a vehicle such as a motor vehicle receives an impact to deploy in an optimal direction by a simple device.